How to Hide Rockon Link Monitor Admin Menus

function plt_hide_rockon_link_monitor_menus() {
	//Hide "Link Monitor".
	remove_menu_page('rockon-link-monitor');
	//Hide "Link Monitor → Broken links".
	remove_submenu_page('rockon-link-monitor', 'rockon-link-monitor');
	//Hide "Link Monitor → Contact Us".
	remove_submenu_page('rockon-link-monitor', 'rockon-link-monitor-contact');
	//Hide "Link Monitor → Add-Ons".
	remove_submenu_page('rockon-link-monitor', 'rockon-link-monitor-addons');
}

add_action('admin_menu', 'plt_hide_rockon_link_monitor_menus', 1000000000);

Where do I put this code?